Al makes good points; all I want to do here is emphasize something that he mentions about speaker sensitivity:
Sensitivity and efficiency are different measurements! Sensitivity is 2.83 volts at 1 meter, efficiency is 1 watt at 1 meter. Now if you have an 8 ohm speaker, then they are the same. But if you have a 4 ohm speaker, watch what happens: 2.83 volts into 4 ohms is **2** watts. So if you have a 90 db sensitivity speaker that is 4 ohms, its efficiency is 3 db less, 87 db.
Conversely, if you have a 16 ohm speaker that is 90 db sensitivity, its efficiency is 93 db.
Tubes do not double power as you cut the impedance in half, and many transistor amps do. So if you are using tubes, you really have to pay attention to the significance of these figures else they will shoot you in the foot rather quickly!
Its my opinion that the sensitivity figure can be misleading, as it often creates the impression that a speaker is more efficient than it really is. Now whether we like it or not, the amount of power that the amp can make into the load is what we are talking about here- and not all transistor amps double power as the impedance is halved (and certainly no tube amp does...).
My room at home is about 17' x 22'; with 87 db the power levels for any serious dynamics gets a bit crazy- this is why I argue for efficiency if you can get it without compromising resolution and bandwidth, and quite often that is very possible. I make this point as there is a tube amp involved; if you really want to get the performance out of tubes, you owe it to yourself to use them with speakers that work easily with them. Maybe a poor analogy; but this is something like putting decent tires on a sports car that you intend to drive hard...
Sensitivity and efficiency are different measurements! Sensitivity is 2.83 volts at 1 meter, efficiency is 1 watt at 1 meter. Now if you have an 8 ohm speaker, then they are the same. But if you have a 4 ohm speaker, watch what happens: 2.83 volts into 4 ohms is **2** watts. So if you have a 90 db sensitivity speaker that is 4 ohms, its efficiency is 3 db less, 87 db.
Conversely, if you have a 16 ohm speaker that is 90 db sensitivity, its efficiency is 93 db.
Tubes do not double power as you cut the impedance in half, and many transistor amps do. So if you are using tubes, you really have to pay attention to the significance of these figures else they will shoot you in the foot rather quickly!
Its my opinion that the sensitivity figure can be misleading, as it often creates the impression that a speaker is more efficient than it really is. Now whether we like it or not, the amount of power that the amp can make into the load is what we are talking about here- and not all transistor amps double power as the impedance is halved (and certainly no tube amp does...).
My room at home is about 17' x 22'; with 87 db the power levels for any serious dynamics gets a bit crazy- this is why I argue for efficiency if you can get it without compromising resolution and bandwidth, and quite often that is very possible. I make this point as there is a tube amp involved; if you really want to get the performance out of tubes, you owe it to yourself to use them with speakers that work easily with them. Maybe a poor analogy; but this is something like putting decent tires on a sports car that you intend to drive hard...